The work planned is a study of junctional cell-to-cell communication in cancer cells. The study will compare the permeability properties of the cell junctions in malignant cells in culture with those of normal counterparts, in a search for possible junctional permeability deviations associated with malignancy and their underlying mechanisms. The study will encompass a broad variety of malignant cell types--transformed by virus (including temperature-sensitive mutants) and tumor cells. The main experimental approaches will use fluorescent linear peptides and oligosaccharides for junctional permeability probings; electrophysiological techniques for measurements of cell-cell coupling and for measurement of intracellular Ca2+ activity; and electron-microscopy for complementing studies of junctional structure.